Heresy is any belief or theory that is strongly at variance with established beliefs or customs, particularly the accepted beliefs or religious law of a religious organization. A heretic is a proponent of heresy. Heresy in Christianity, Judaism, and Islam has at times been met with censure ranging from excommunication to the death penalty. Heresy is distinct from apostasy, which is the explicit renunciation of one's religion, principles or cause; and from blasphemy, which is an impious utterance or action concerning God or sacred things. Heresiology is the study of heresy. Source: Wikipedia (en)